If you're getting proper keep-alives in Firefox then there has to be a BrowserMatch setting somewhere in the configs that is breaking stuff. What does the BrowserMatch in the ssl vhost look like? It might be worth narrowing it if it covers ALL IE browsers and only have it apply for IE5 and below to see if that rule is getting hit for some reason (or just remove it temporarily to test).

I have an Red Hat Apache server that seems to be stuck with Keep-Alive off...even though I've gone through this forum and made several changes that solved most similar issues. Here is the site on the server I am using to test:http://www.celiac.com

I've made the following changes--note that I didn't see anything in this site's .htaccess or celiac.conf files:

Yes, I do use https so need that to continue working...and I've not commented them out yet. I'll give that a try and report back. Would commenting these out for a few minutes be something that you would do during the day on a busy site with an https shopping cart? Sorry, but I just don't really know what the negative impact could be on an end user...
PS - would you happen to know the exact 'grep' commands needed to track down other hidden sources of BrowserMatch or SetEnvIf User-Agent in my system...or do you think I've already mentioned the most probable places to look?

For my own sanity, as I am really a server amateur (even though I've been managing this on my own for about 7 years), can I assume a restart of apache is all that is needed to make these config changes go live?

I don't know the exact grep commands for force-response and downgrade...would you be able to post them here for me (sorry!)?

Load balancer or reverse proxy...I am not sure about this. What would be the best way to determine this?

As for the config setting they are:
KeepAlive On
MaxKeepAliveRequests 100
KeepAliveTimeout 15

Just be careful not to do it in a huge directory tree because it will recursively scan all sub-directories too (/etc/apache2/ would be a good place to do it if that is where your apache configs are).

An apache restart will take care of it but if you mess up the config apache won't start so your server will be down until you fix whatever is wrong in the configs.

As far as load balancer goes, usually if you're not sure then there isn't one in place. Did you initially configure the server or did someone else do it? If it is a single server (or VPS), apache is listening on port 80 for your website and the server IP is the same as the IP address for your site then it's pretty safe to say there isn't one.

As for my server, I did not configure it, it was a package offered by OLM. It is my understanding that it is a standalone server that I control, but is set up with it's own separate IP, and all sites on it can be set up to be either name based or IP based through the Ensim Pro control panel. The site in question is an IP-based site that listens on port 80, but again, the server itself has its own IP.